The availability of aerosol creams and toppings has led to their widespread use in customising desserts and beverages. Ice cream and similar frozen aerated products are often used as alternatives to whipped creams and toppings. The lack of such a product in an aerosol form, however, has meant that it is not possible to apply frozen products in such a controlled and convenient manner as whipped creams and thus limits their versatility. In addition, there has long been a need to provide soft-serve ice cream, a popular out-of-home dessert, in a form where it may be dispensed at home directly on removal from the freezer.
Aerosol systems for dispensing frozen aerated products have been proposed in the past. WO 03/096821 discloses such a system wherein the frozen aerated product is provided in a container, the container having at least two compartments and the frozen aerated product containing freezing point depressants in an amount between 20% and 40% w/w and having a number average molecular weight <M>n dependant on the fat level in the frozen aerated product. The container may be provided with a valve having an N value (ratio of the flow rate of a Newtonian fluid and the viscosity to the pressure drop across the valve) of between 5×10^(−11) m3 and 1×10^(−7) m3. Furthermore, embodiments are described with flow rates up to 4.7 g s−1 at −18° C.
Such technology allows for a frozen aerated product that may be dispensed from an aerosol can at the temperature of a domestic freezer (−18 to −22° C.) and represents a significant improvement over prior technologies. We have found, however, that there exists a need for further improvements in aerosol systems for dispensing frozen aerated products. In particular, the rate at which product is dispensed with the existing technology requires the user to hold the valve open for a considerable length of time. In addition, if conventional aerosol valves are used then the actuation force is found to be undesirably high for one-fingered actuation. Thus the products may not be applied to all of the applications for which aerosol whipped creams and toppings are used.
There is thus a need for an improved aerosol system for dispensing aerated products in a convenient manner at a temperature of a domestic freezer.
It has been found that it is possible to achieve such a goal by providing a frozen aerated product in a container equipped with a valve with a flow rate in a specific range. Furthermore, by careful design of the valve it has been found possible to provide valves suitable for dispensing viscous products from aerosol cans at high rates but which have low opening and actuating forces.
Tests and Definitions
Pressure
In the description ‘barg’ means ‘bar gauge’ (i.e., relative to 1 atm) and the pressure was measured at a temperature of −10° C.
Flow Rate
The flow rate of a valve arranged to dispense a frozen aerated product from a container is defined as the mass flow rate at which the frozen aerated product, having a temperature of −18° C., is discharged through the fully open valve to atmospheric pressure.
The flow rate is determined as follows.
Four specimens of a frozen aerated product in a container equipped with a valve and actuator are tempered at −18° C. for 24 hours. The actuator is designed to avoid any restriction of the flow of product following exiting from the valve such that any measurement of flow rate is a true measurement of flow through the valve alone. Each specimen is then taken from the −18° C. store, around 10 g of product dispensed through the valve and actuator and then the specimen returned to the −18° C. store. This pre-test dispensing ensures that the valve and actuator are charged fully with product while the small volume dispensed ensures that the pressure in the container is reduced only by a negligible amount. The cans are stored for a further 24 hours at −18° C. prior to testing.
For testing, a can is removed from the −18° C. store and the valve immediately actuated for a total of 10 s. This actuation is such that the valve is open to its full extent. The product dispensed during this actuation is collected and weighed. The flow rate for a specimen is then calculated by dividing the mass collected by 10 s. The process is then repeated for the other three specimens. The flow rate of the valve is taken to be the mean of the flow rate of the four specimens and the uncertainties quoted are the corresponding 95% confidence intervals.
Definition of Constriction
A constriction is defined as channel or orifice through which a product dispensed through a valve must pass. The cross-sectional area of such a constriction is the area of the channel or orifice, in a plane normal to the direction of flow of the product through the constriction during dispensing.
Opening Force
The opening force of a valve arranged to dispense a frozen aerated product from a container is defined as the minimum force that can be applied directly to the valve in order to open the valve to its full extent at a rate of 100 mm min−1, wherein the frozen aerated product has a temperature of −22° C.
The opening force is determined as follows.
Four specimens of a frozen aerated product in a container equipped with a valve (but not an actuator) are tested. The specimens are tempered at −22° C. for 24 hours prior to testing.
For testing, a can is removed from the −22° C. store and immediately secured in a cradle located in the environmental chamber of an Instron™ Universal Testing Machine. The cradle is designed to ensure that the container is static during testing and that the valve is located such that lowering or raising of the cross-head of the Instron™ opens the valve. The environmental chamber is supplied with liquid nitrogen and held at a constant temperature of −22° C. The cross-head is designed to allow full actuation without restricting the flow of product out of the valve. The cross-head is moved until it is around 0.5 mm away from touching the valve stem (or other valve member arranged to open the valve on application of a force) and the force meter on the testing machine is zeroed. The cross-head is then moved at a rate of 100 mm min−1 until the valve is opened to its full extent, the force applied being recorded every 0.1 s−1. The opening force for the specimen is taken to be the maximum force applied during the test. The process is then repeated for the other three specimens. The opening force of the valve is taken to be the mean of the opening force of the four specimens and the uncertainties quoted are the corresponding 95% confidence intervals.
Actuation Force
The actuation force of an actuating member provided to a valve arranged to dispense a frozen aerated product from a container is defined as the minimum force that can be applied directly to the actuating member in order to open the valve to its full extent when the member is moved at a rate of 100 mm min−1, wherein the frozen aerated product has a temperature of −22° C.
The actuation force is determined in an identical manner to that described for determining the opening force with two exceptions. Firstly, the valves are equipped with actuators. Secondly, the cross-head used is a simple cylinder and rather than acting directly on the valve stem (or other valve member arranged to open the valve on application of a force), the cross-head is moved onto the actuator during the test in order to mimic the action of the finger of a user when dispensing the product.
Average Molecular Weight
The average molecular weight for a mixture of freezing point depressants (fdps) is defined by the number average molecular weight <M>n (equation 1). Where wi is the mass of species i, Mi is the molar mass of species i and Ni is the number of moles of species i of molar mass Mi.
                              <          M          ⁢                      >            n                          =                                            ∑                              w                i                                                    ∑                              (                                                      w                    i                                    /                                      M                    i                                                  )                                              =                                    ∑                                                N                  i                                ⁢                                  M                  i                                                                    ∑                              N                i                                                                        Equation        ⁢                                  ⁢        1            Freezing Point Depressants
Freezing point depressants (fpds) as defined in this invention consist in:                Monosaccharides and disaccharides.        Oligosaccharides containing from 3 to ten monosaccharide units joined in glycosidic linkage.        Corn syrups with a dextrose equivalent (DE) of greater than 20 preferably >40 and more preferably >60. Corn syrups are complex multi-component sugar mixtures and the dextrose equivalent is a common industrial means of classification. Since they are complex mixtures their number average molecular weight <M>n can be calculated from the equation below. (Journal of Food Engineering, 33 (1997) 221-226).        
  DE  =      18016          <      M      ⁢              >        n                            Erythritol, arabitol, glycerol, xylitol, sorbitol, mannitol, lactitol and malitol.Definition of Overrun        
Overrun is defined by the following equation
  OR  =                                                                        volume                ⁢                                                                  ⁢                of                ⁢                                                                  ⁢                frozen                ⁢                                                                  ⁢                aerated                ⁢                                                                  ⁢                product                            -                                                                          volume              ⁢                                                          ⁢              of              ⁢                                                          ⁢              premix              ⁢                                                          ⁢              at              ⁢                                                          ⁢              ambient              ⁢                                                          ⁢              temp                                                  volume        ⁢                                  ⁢        of        ⁢                                  ⁢        premix        ⁢                                  ⁢        at        ⁢                                  ⁢        ambient        ⁢                                  ⁢        temp              ×    100  
It is measured at atmospheric pressure.
Definition of R Value
For a valve arranged to dispense a pressurised product, which is opened by the application of an opening force to one or other of a valve stem and a first member, a parameter R is defined by the following equation:R=Am/Ab.
Wherein Ab is the maximum area of a cross-section of the stem bore in a plane normal to the direction of flow of the product during dispensing and Am is the area of an orthographic projection on to a plane normal to the direction of the opening force of those solid portions, on which with the valve in a closed position the pressure of the product acts in a direction opposite to the direction of the opening force, of the one or other of the valve stem and the first member to which the opening force is applied.